1. Field of the Invention
The present invention pertains to data communications and in particular to a communication interface for processing bisynchronous protocol communications.
2. Description of Prior Art
Digital data communication between remote terminals is coming into widespread use especially for office and business communications. This communication is typically transmitted through telephone lines or equivalent narrow band communication channels. Each of the terminals involved in the communication usually utilizes a modem for transmission of the digital data over the communication channel. However, in the development of data communications a number of separate and incompatible communication protocols have been adopted. A terminal which is designed to operate with one protocol is limited to communicating only with other terminals which utilize the same protocol. The existence of the multiple and incompatible protocols constitutes a serious impediment to the expansion of business and commercial data communications.
Bisynchronous protocol is frequently used in business and commercial communications. The standard circuit designed for use with this protocol does not include clock generation circuitry but depends upon a clock signal which is derived from the modem. The bisynchronous protocol has traditionally been associated only with self clocked medium speed modem operations, but there are requirements for bisynchronous protocol communication using non-clocked modems. Therefore, there exists a need for a bisynchronous protocol communication circuit which can operate with a non-clock-generating modem.